1. Field of the Invention
The present invention relates to a platform door device applied to a station platform etc. More particularly, it relates to a platform door device in which two movable fences, which are provided along the side edge of a station platform for railroad cars and each supported movably by a support member, move relative to each other in the car running direction on the platform to open and close a passage between the platform side and the car side.
2. Description of Related Art
Among station platforms for railroad cars, the number of platforms each equipped with a platform door device provided with a movable fence has increased to prevent accidents such as passengers falling onto the railway tracks, or passengers coming into contact with a car. Such a platform door device is usually constructed so that two movable fences provided along the side edge of the platform are supported movably by support members, and the two movable fences move relative to each other in the car running direction to open and close a passage between the platform side and the car side.
FIGS. 7 to 9 show a platform door device disclosed in Patent Document 1 (Japanese Patent Provisional Publication No. 2004-131008). FIG. 7 is a general perspective view, FIG. 8 is a side view of a principal portion, showing one side of a movable fence, and FIG. 9 is a sectional view taken along the line X-X of FIG. 8.
In FIGS. 7 to 9, reference numeral 1 denotes a platform door, in which two movable fences 5 are supported so as to be slidable in the direction indicated by arrows in FIG. 7 in such a manner as to overlap with each other in the longitudinal direction (the direction perpendicular to a side edge 3 of a platform 2, namely, the direction perpendicular to the car running direction) of a fence member 4 erected at the side edge 3 of the platform 2. The movable fence 5 goes in and out through a gateway 7 formed in each side surface portion 6 of the fence member 4.
As shown in FIG. 8, the movable fence 5 is rotatably provided with two guide roller members 10 on the upper and lower sides, and two guide rails 11 are fixed to the upper and lower sides of the fence member 4. By the rolling motion of the roller members 10 along the guide rails 11, the two movable fences 5 can be moved smoothly in a reciprocating manner with respect to the fence member 4.
Also, the fence member 4 is provided with drive motors 12, and a pinion 13 is provided on the output shaft of each of the drive motors 12. On the other hand, in a central portion in the height direction of the movable fence 5, a rack 14 engaging with the pinion 13 is provided in parallel with the guide rails 11. Therefore, when the drive motor 12 is rotated, the movable fence 5 is moved in a reciprocating manner as indicated by an arrow in FIG. 7 by the engagement of the pinion 13 with the rack 14.
Also, as shown in FIG. 9, within the fence member 4, two support plates 20 and 21 erected on the platform 3 are arranged. On the side surfaces of the support plates 20 and 21, the drive motor 12 is installed.
Further, the fence member 4 is provided with a cover 22, one end portion of which is fixed at the upper end of the support plate 21. The whole of the support plates 20 and 21 and the movable fences 5 that go into and out of the fence member 4 is covered with the cover 22 so that a relatively moving portion between the support plates 20 and 21 and the movable fences 5 is not exposed to the outside, and dust etc. is prevented from entering into the relatively moving portion from the outside. The gateways 7 are open in side surface portions 6 of the cover 22 so that the movable fences 5 go in and out through the gateways 7.
The above-described conventional platform door device has problems as described below.
In the above-described related art, the platform door device has a construction such that the fence member 4 is erected along the side edge 3 of the platform 2; the movable fences 5 are arranged in parallel with each other in the side portions of the two support plates 20 and 21; the roller members 10, the drive motors 12, and the like are arranged between the support plates 20 and 21 and the movable fences 5; and further the elements within the fence member 4 are covered with the cover 22. Therefore, the thickness of the fence member 4, namely, a width W0 (refer to FIG. 9) in the direction perpendicular to the side edge 3 of the platform 2 increases undesirably.
Thereupon, in the above-described related art, the increase in the thickness W0 of the fence member 4 obstructs the space along the side edge 3 of the platform 2, and hence hinders passengers and other people from passing. Also, on a platform 2 with a narrow width, the platform door device having the above-described construction cannot be adopted.